1. Field of the Invention
The invention relates to an electric power steering system that determines a steering state of a steering wheel on the basis of at least one of detected current and voltage of a motor that applies assist force to a steering system, and a steering speed of the steering wheel.
2. Description of Related Art
An electric power steering system described in Japanese Patent Application Publication No. 2002-120741 (JP-A-2002-120741) determines that the steering state of a steering wheel is a retained state on the basis of the fact that the steering speed of the steering wheel is lower than a predetermined value. In addition, when, in addition to the determination that the steering state is a retained state, the determination that the current of the motor is smaller than a predetermined value is made, it is determined that the steering state of the steering wheel is a neutral state.
When the steering state of the steering wheel is maintained in the neutral state in a situation where side wind acts on the vehicle, relatively large assist force is applied from the motor to the steering system and then the current of the motor may be larger than the predetermined value. However, according to the method of determining a steering state, described in JP-A-2002-120741, when the current of the motor is larger than or equal to the predetermined value although the steering state of the steering wheel is the neutral state, it may be determined that the steering state is a retained state.